MAIN OBJECTIVES IN 1997
HARBOUR PORPOISE RELEASE PROGRAM
AN AGING FLEET
Field research ran from July 8 to September 26. Each day the weather permitted, we monitored all of the weirs on the northern and eastern sides of Grand Manan for the presence of porpoises. The number of entrapped harbour porpoises was higher than in 1996 approaching more normal entrapment figures for other years (Table 1). We do not know why the entrapment rate fluctuates from year to year but we assume that it is related to herring densities in near-shore waters. This has increased our awareness of the dynamic nature and complex interactions between porpoises, their environment and their prey, and highlighted the need to consider these issues concurrently.
We successfully released 20 of 22 porpoises, two died during seining process. We also had three minke whales in weirs, all successfully released. Each of the whale releases was accomplished using our specially designed marine mammal seine and we attributed our success to the use of this net. In the past minke whales often became entangled in herring seines and died in weirs but we have now developed a protocol that can be used to ensure their safe release in coming years.
Five porpoises were fitted with satellite tags. The transmitters lasted for 42, 92, 122, 144, and 171days. The track data for three of the porpoises, including maps can be found on WhaleNet .
The satellite tracks represent important steps forward in understanding how harbour porpoises utilize habitat in summer and fall. As well as confirming some previous conclusions, we have identified some new important features of harbour porpoise movements from these tracks.
Unfortunately, we did not experience similar success with the foraging study. Although we deployed three self-releasing time-depth recorders on harbour porpoises we were unable to recover any of these units. This was in sharp contrast to our previous TDR study in which we recovered all nine units we deployed. After these initial failures we chose to suspend further deployments until these problems could be resolved. It was discovered that a design flaw in the floatation component of the package prevented them from floating when the packs came loose. We believe the floatation material compressed when the porpoises dived to depth making the packs negatively buoyant.
During the TDR deployments we were able to follow the tagged porpoises with relative ease and the protocol we developed worked very well during each of the follows. The packs had a special magnesium linkage which slowly dissolved in the seawater allowing the packs to release from the porpoises after 10-12 hours. In each deployment the packs detached from the porpoise close to the predicted release time. We are confident that with the modification that are currently underway to the design, we will be successful in our deployments during 1998.
Although we replaced one of our old boats a couple of years ago, we are now in desperate need of replacing an aging speed boat. We use the speed boat to check herring weirs daily for the HARBOUR PORPOISE RELEASE PROGRAM, and as a second seine boat when we are needed at more than one herring weir or when there are numerous porpoises in one weir. We have applied for funding for both boat and engine and so far have had been awarded funding from the George Cedric Metcalf Charitable Foundation and the T.R. Meighen Foundation. We are awaiting one additional source before any purchases can be made.
About the Grand Manan Whale and Seabird Research Station Research Station
The Grand Manan Whale & Seabird Research Station (GMWSRS) is a non-profit research facility located in North Head. The GMWSRS was founded in 1981 by the late Dr. David Gaskin, a professor at the University of Guelph, Ontario and a pioneer of harbour porpoise research on Canada's east coast. Since 1981, the research station has conducted research on harbour porpoises, right whales, seals and seabirds in the Grand Manan Archipelago.
A GOOD WINTER AND WE'LL SEE YOU NEXT SUMMER!
Harbour Porpoise Research: 1997 | 1998
Harbour Porpoise Release Program - home page